I am trying to determine when rail spacing of 4 3/8" (inches) applies. The 2006 IRC 312.2 says "required guards on open sides of stairways, (then other things), shall have intermediate rails which do not allow the passage of a sphere 4" or more in diameter.

As you know, it also goes onto 2 exceptions. The second exception being, "openings for required guards on the sides of stair treads shall not allow a sphere of 4 3/8" to pass through.

I realize that guards can be handrails, as long as certain requirements are met from 311 (grip, height, etc.).

The 2006 IRC states that section slightly differently, and that difference makes all the difference when reading it.

From the 2006 IRC. (underlining and bold are mine) - R312.2 Guard opening limitations. Required guards on open sides of stairways, raised floor areas, balconies and porches shall have intermediate rails or ornamental closures which do not allow passage of a sphere 4 inches (102 mm) or more in diameter. - - Exceptions: - - - 1. The triangular openings formed by the riser, tread and bottom rail of a guard at the open side of a stairway are permitted to be of such a size that a sphere 6 inches (152 mm) cannot pass through. - - - 2. Openings for required guards on the sides of stair treads shall not allow a sphere 4 3/8 inches (107 mm) to pass through.

The maximum allowable size for a sphere is 4 inches, except ... - except at that triangular area = 6 inches - except at the side of the stair treads = 4-3/8 inches

If you code states it differently, would you please post the exact wording and the code it is from? Thank you.

Mine says what yours says, I just abbreviated it because my confusion is coming from 'guards on open sides of stairways' versus 'guards on the sides of stair treads'.

I think this is what I'm not understanding. In my mind both of these describe guards for for guardrails, where the guardrail is also the handrail (so long as it meets 311).

It seems this is where the key is, but I'm not 'seeing' the difference between the two. Does this have to do with the rails that connect to the guard/handrail at the top, but do not attach directly to a stair, but rather a rail parallel to the top of the guard/ handrail?

jakeg wrote:Mine says what yours says, I just abbreviated it because my confusion is coming from 'guards on open sides of stairways' versus 'guards on the sides of stair treads'.

Now I think I understand what you are asking.

A "stair" is one or more risers - that is by definition in the codes, and all "stairs" require a top landing and a bottom landing, which are not included in the term "stair".

After that, some of the definitions in the code are missing, however, the terms are referenced as though they are defined and known.

A "flight of stairs" is similar to a "stair" except that the bottom landing and top landing are included, i.e., a "flight of stairs" consists of a bottom landing, a top landing, and one or more risers between the two.

A "stairway", also sometimes referred to as a "stair", is one or more "flights of stairs" - there could be a bottom landing, a flight of stairs, an intermediate landing, another flight of stairs, and then a top landing, with both flights of stairs using the intermediate landing as a common landing.

Then there is the "guards on the sides of stair treads" wording which is referring to a "stair" as having more than one riser, which requires a tread between each riser.

Thus there are two distinct guards being referenced: a) guards along flat walking surfaces such as porches, balconies, raised floor areas, and landings within a stairway - where the walkings surfaces and guards are essentially level; b) guards along the sloping walkway portion of the stairway, i.e., where the riser/tread/riser/tread/riser/etc. are located - these walking surfaces and guards are sloping with the stair.

Guards falling within a) above have a maximum allowed opening size of *less than* 4 inches. I clarify that as a 4 inch sphere *is not allowed to pass through*, meaning the opening must be *less that 4 inches*.

Guards falling within b) above have those two exceptions to the 4 inch limitation: 1) the triangular opening at the tread/riser/bottom rail is *not allowed to pass* a 6 inch sphere; 2) the in-fill area of the guard is *not allowed to pass* a 4-3/8 inch sphere. When a guard does not have a bottom rail, such as where the balusters go from the tread to the guard top rail, then there is no triangular opening to except out.